Invaluable means so useful that its worth cannot be priced. Invaluable help, an invaluable resource, absolutely invaluable.
The prefix trips people up: invaluable does not mean without value, it means beyond valuing — the same logic as priceless. Its actual opposite is worthless. It is warm praise, used of help, advice and experience rather than of objects. Note valuable, which is weaker; and that invaluable is one of a small set where in- means beyond rather than not, alongside inflammable, which causes rather more trouble.
1adjectiveinvaluableSo useful that its worth cannot be priced.
“Her knowledge of the local area proved invaluable to the new team.”
synonyms: priceless, indispensable
invaluable is a quality of great worth.
Also accepted in games: priceless
In- plus valuable, on the pattern of priceless — the prefix here means beyond rather than not. Latin valere, to be strong or worth, gives value, valid and prevail.
From in + valuable (compare priceless). unvaluable.
Etymology from Wiktionary, CC BY-SA